30 Questions
Which type of microorganisms are too small to be seen by the human eye?
Viruses
What is the characteristic genomic material of prokaryotes (bacteria)?
Only DNA, not surrounded by a nuclear membrane
Which type of microorganism has a complex cell wall with peptidoglycan and other components?
Bacteria
Which microorganism is characterized by 70S ribosomes and flagella with a simple structure?
Bacteria
Which type of microorganism is considered acellular?
Viruses
Which microorganism is characterized by different organelles separated by internal membranes?
Protozoa
What is the purpose of the Kirby-Bauer disk diffusion test?
To measure the diameters of inhibition growth zones
What does MIC stand for in the context of antimicrobial drugs?
Minimum Inhibitory Concentration
How is the MIC determined in the Etest (Antimicrobial Gradient Method)?
By depositing a strip with an increasing concentration gradient of the antimicrobial agent on the agar surface
What is the purpose of converting inhibition zone diameters or MIC values into SIR categories?
To define resistance/sensitivity of antimicrobial drugs
How are antibiotics classified?
By their mechanism of action
Which organization publishes breakpoints for clinically relevant organisms?
Clinical and Laboratory Standards Institute (CLSI)
Which bacterial species are examples of biofilm formers?
Staphylococcus aureus, Pseudomonas aeruginosa, Bacillus cereus
What is the purpose of endospore formation by some Gram-positive bacteria?
As a survival mechanism when growth conditions become unfavorable
How do broad-spectrum antibiotics differ from narrow-spectrum antibiotics?
Broad-spectrum antibiotics inhibit a wide variety of bacteria, while narrow-spectrum drugs are effective against a limited range
What is the minimal inhibitory concentration (MIC) of antimicrobial drugs?
The lowest concentration that inhibits growth
How is the minimal lethal concentration (MLC) defined for antimicrobial drugs?
The lowest concentration that kills the pathogen
Which method is used to determine minimal inhibitory concentrations (MICs)?
Broth dilution method
What is the fundamental difference in bacterial biochemistry and structure that distinguishes gram-positive and gram-negative bacteria?
Thickness of the peptidoglycan layer
Which component of the bacterial cell wall provides structural support and rigidity?
Peptidoglycan
What makes mycobacteria resistant to many antibiotics and disinfectants?
High percentage of lipids in the cell wall
Which type of bacteria has unique cell walls made of waxy, hydrophobic coats with mycolic acids and arabinogalactan polysaccharides?
Mycobacteria
Which type of bacteria lacks cell walls and only has plasma membranes?
Mycoplasma
What is the primary function of lipopolysaccharide (LPS) in gram-negative bacteria?
Creating a permeability barrier
What is the role of capsules in bacteria?
Assist in attachment to surfaces, role in development and maintenance of biofilms
Which type of metabolism is associated with the production of reactive oxygen species (ROS) through aerobic respiration?
Aerobic respiration
What is the function of Type IV (T4SS) bacterial secretion system?
Mediate DNA uptake
What is a primary function of flagella in bacteria?
Function in motility
Which phase of bacterial growth experiences zero growth rate and essential nutrients being used up?
Stationary phase
What is the process that involves DNA replication, cell elongation, septum formation, and cell separation in bacteria?
Binary fission
Study Notes
- Bacterial secretion systems are molecular complexes inserted in the bacterial envelope, specifically exporting toxins or effectors to the outside environment or to another cell.
- Three main types of secretion systems: Type III (T3SS), Type IV (T4SS), and Type VI (T6SS).
- The text focuses on the cell envelope and components outside of it, specifically capsules, pili, and flagella.
- The cell envelope is composed of a cell wall and other membranes and structures that surround and protect the cytoplasm.
- Capsules, often composed of polysaccharides, are structures outside the cell wall that assist in attachment to surfaces, role in development and maintenance of biofilms, protect from desiccation, and exclude viruses and detergents.
- Capsules are a key component of numerous vaccines against encapsulated pathogens, such as Neisseria meningitidis serotypes A, C, W, Y polysaccharide vaccine.
- Pili are short, thin, hairlike protein appendages that can mediate attachment to surfaces, motility, and DNA uptake. Sex pili are longer, thicker, and less numerous and are required for genetic exchange between bacteria.
- Flagella are threadlike, locomotor appendages extending outward from the plasma membrane and cell wall, found in both Gram-positive and Gram-negative bacteria, and function in motility, attachment to surfaces, and may be virulence factors.
- Two basic types of metabolism for pathogenic bacteria are alcohols and acids production through fermentation, and nitrate or sulfate respiration.
- Aerobic respiration generates reactive oxygen species (ROS), which must be detoxified by protective enzymes such as catalase, peroxidase, and superoxide dismutase.
- The text discusses the growth of bacteria through binary fission, which involves DNA replication, cell elongation, septum formation, and cell separation, and has a generation time that depends on several factors.
- Bacterial metabolism goes through various phases, including lag phase, exponential phase, stationary phase, and death.
- In exponential phase, cells are typically in the healthiest state and experience the most rapid growth.
- In stationary phase, growth rate is zero, some cells grow while others die, essential nutrients are used up, and waste products accumulate or culture runs out of O2.
- Aerobic and aerotolerant organisms contain protective enzymes to detoxify reactive oxygen species, while obligate anaerobes lack or have very low quantities of such enzymes.
Test your knowledge about bacterial secretion systems with this quiz. Explore the different types of secretion systems, their components, and functions.
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